Swimming pools subject to winter conditions are winterized to avoid damage to pipes caused when the water freezes.
Part of the winterizing process is to lower the level of the water within the pool and to drain various piping used in the circulation and heating system, such as from the filter and heater. Some of the pipes cannot be fully drained, for example, skimmers used in swimming pools have one line which is connected to the drain of the pool and the level of water within this line drops with, and is equal to, the level of water in the pool. By dropping the pool water level, the water in the pipe is lowered, however, it is desirable to maintain a certain amount of water in the pool to avoid inward collapsing of the pool, during a frost push, for example. With a lower pool level, damage can occur in the pipe connecting the skimmer to the drain. If damage does occur in this pipe, access to the pipe must be obtained and a replacement pipe inserted. This can be a substantial problem with respect to inground pools and can be relatively expensive to repair.